Hydride ion continuum hides absorption signatures in the NIRPS near-infrared transmission spectrum of the ultra-hot gas giant WASP-189b
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| Format: | Preprint |
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2025
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| author | Vaulato, Valentina Pelletier, Stefan Ehrenreich, David Allart, Romain Cristo, Eduardo Steiner, Michal Dumusque, Xavier Chakraborty, Hritam Lendl, Monika Srivastava, Avidaan Artigau, Étienne Baron, Frédérique Barros, C. Susana Benneke, Björn Bonfils, Xavier Bouchy, François Bryan, Marta Martins, Bruno L. Canto Cloutier, Ryan Cook, Neil J. Cowan, Nicolas B. De Medeiros, Jose Renan Delfosse, Xavier Doyon, René Hernández, I. Jonay González Lafrenière, David Leão, Izan de Castro Lovis, Christophe Malo, Lison Melo, Claudio Mignon, Lucile Mordasini, Christoph Pepe, Franceso Rebolo, Rafael Rowe, Jason Santos, Nuno C. Ségransan, Damien Mascareño, Alejandro Suárez Udry, Stéphane Valencia, Diana Wade, Gregg Moulla, Khaled Al Bazinet, Luc Bourrier, Vincent Cadieux, Charles Carteret, Yann Silva, Ana Rita Costa Darveau-Bernier, Antoine Dauplaise, Laurie Gomes, Roseane de Lima Delisle, Jean-Baptiste Forveille, Thierry Frensch, Yolanda Gagné, Jonathan Genest, Frédéric da Silva, João Gomes Grieves, Nolan Hobson, Melissa J. Krishnamurthy, Vigneshwaran L'Heureux, Alexandrine Lamontagne, Pierrot Larue, Pierre Lim, Olivia Curto, Gaspare Lo Messamah, Lina Messias, Yury S. Moranta, Leslie Mounzer, Dany Nari, Nicola Osborn, Ares Parc, Léna Piaulet, Caroline Plotnykov, Mykhaylo Psaridi, Angelica Stefanov, Atanas K. Teixeira, Márcio A. Vandal, Thomas Wardenier, Joost P. Weisserman, Drew Yariv, Vincent |
| author_facet | Vaulato, Valentina Pelletier, Stefan Ehrenreich, David Allart, Romain Cristo, Eduardo Steiner, Michal Dumusque, Xavier Chakraborty, Hritam Lendl, Monika Srivastava, Avidaan Artigau, Étienne Baron, Frédérique Barros, C. Susana Benneke, Björn Bonfils, Xavier Bouchy, François Bryan, Marta Martins, Bruno L. Canto Cloutier, Ryan Cook, Neil J. Cowan, Nicolas B. De Medeiros, Jose Renan Delfosse, Xavier Doyon, René Hernández, I. Jonay González Lafrenière, David Leão, Izan de Castro Lovis, Christophe Malo, Lison Melo, Claudio Mignon, Lucile Mordasini, Christoph Pepe, Franceso Rebolo, Rafael Rowe, Jason Santos, Nuno C. Ségransan, Damien Mascareño, Alejandro Suárez Udry, Stéphane Valencia, Diana Wade, Gregg Moulla, Khaled Al Bazinet, Luc Bourrier, Vincent Cadieux, Charles Carteret, Yann Silva, Ana Rita Costa Darveau-Bernier, Antoine Dauplaise, Laurie Gomes, Roseane de Lima Delisle, Jean-Baptiste Forveille, Thierry Frensch, Yolanda Gagné, Jonathan Genest, Frédéric da Silva, João Gomes Grieves, Nolan Hobson, Melissa J. Krishnamurthy, Vigneshwaran L'Heureux, Alexandrine Lamontagne, Pierrot Larue, Pierre Lim, Olivia Curto, Gaspare Lo Messamah, Lina Messias, Yury S. Moranta, Leslie Mounzer, Dany Nari, Nicola Osborn, Ares Parc, Léna Piaulet, Caroline Plotnykov, Mykhaylo Psaridi, Angelica Stefanov, Atanas K. Teixeira, Márcio A. Vandal, Thomas Wardenier, Joost P. Weisserman, Drew Yariv, Vincent |
| contents | Ultra-hot Jupiters showcase extreme atmospheric conditions, including molecular dissociation, ionisation, and significant day-to-night temperature contrasts. Their close proximity to host stars subjects them to intense stellar irradiation, driving high temperatures where hydride ions (H$^-$) significantly contribute to opacity, potentially obscuring metal features in near-infrared transmission spectra. We investigate the atmosphere of WASP-189b, targeting atomic, ionic, and molecular species (H, He, Fe, Ti, V, Mn, Na, Mg, Ca, Cr, Ni, Y, Ba, Sc, Fe$^+$, Ti$^+$, TiO, H$_2$O, CO, and OH), focusing on (i) the role of H$^-$ as a source of continuum opacity, and (ii) the relative hydride-to-Fe abundance using joint optical and near-infrared data. We present two transits of WASP-189b gathered simultaneously in the optical with HARPS and near-infrared with NIRPS, supported by photometric light curves from EulerCam and ExTrA. Transmission spectra were analysed via cross-correlation to detect absorption features and enhance the signal-to-noise ratio. Atmospheric retrievals quantified relative abundances by fitting overall metallicity and proxies for TiO, H$^-$, and e$^-$. Only atomic iron is detected in HARPS data (S/N ~5.5), but not in NIRPS, likely due to H$^-$ continuum dampening. Retrievals on HARPS-only and HARPS+NIRPS suggest the hydride-to-Fe ratio exceeds equilibrium predictions by about 0.5 dex, hinting at strong hydrogen ionisation. Including NIRPS data helps constrain H$^-$ abundance and set an upper limit on free electron density, unconstrained in HARPS-only data. These results emphasise H$^-$ as a significant continuum opacity source impeding detection of planetary absorption features in WASP-189b's near-infrared transmission spectrum. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2507_21229 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Hydride ion continuum hides absorption signatures in the NIRPS near-infrared transmission spectrum of the ultra-hot gas giant WASP-189b Vaulato, Valentina Pelletier, Stefan Ehrenreich, David Allart, Romain Cristo, Eduardo Steiner, Michal Dumusque, Xavier Chakraborty, Hritam Lendl, Monika Srivastava, Avidaan Artigau, Étienne Baron, Frédérique Barros, C. Susana Benneke, Björn Bonfils, Xavier Bouchy, François Bryan, Marta Martins, Bruno L. Canto Cloutier, Ryan Cook, Neil J. Cowan, Nicolas B. De Medeiros, Jose Renan Delfosse, Xavier Doyon, René Hernández, I. Jonay González Lafrenière, David Leão, Izan de Castro Lovis, Christophe Malo, Lison Melo, Claudio Mignon, Lucile Mordasini, Christoph Pepe, Franceso Rebolo, Rafael Rowe, Jason Santos, Nuno C. Ségransan, Damien Mascareño, Alejandro Suárez Udry, Stéphane Valencia, Diana Wade, Gregg Moulla, Khaled Al Bazinet, Luc Bourrier, Vincent Cadieux, Charles Carteret, Yann Silva, Ana Rita Costa Darveau-Bernier, Antoine Dauplaise, Laurie Gomes, Roseane de Lima Delisle, Jean-Baptiste Forveille, Thierry Frensch, Yolanda Gagné, Jonathan Genest, Frédéric da Silva, João Gomes Grieves, Nolan Hobson, Melissa J. Krishnamurthy, Vigneshwaran L'Heureux, Alexandrine Lamontagne, Pierrot Larue, Pierre Lim, Olivia Curto, Gaspare Lo Messamah, Lina Messias, Yury S. Moranta, Leslie Mounzer, Dany Nari, Nicola Osborn, Ares Parc, Léna Piaulet, Caroline Plotnykov, Mykhaylo Psaridi, Angelica Stefanov, Atanas K. Teixeira, Márcio A. Vandal, Thomas Wardenier, Joost P. Weisserman, Drew Yariv, Vincent Earth and Planetary Astrophysics Ultra-hot Jupiters showcase extreme atmospheric conditions, including molecular dissociation, ionisation, and significant day-to-night temperature contrasts. Their close proximity to host stars subjects them to intense stellar irradiation, driving high temperatures where hydride ions (H$^-$) significantly contribute to opacity, potentially obscuring metal features in near-infrared transmission spectra. We investigate the atmosphere of WASP-189b, targeting atomic, ionic, and molecular species (H, He, Fe, Ti, V, Mn, Na, Mg, Ca, Cr, Ni, Y, Ba, Sc, Fe$^+$, Ti$^+$, TiO, H$_2$O, CO, and OH), focusing on (i) the role of H$^-$ as a source of continuum opacity, and (ii) the relative hydride-to-Fe abundance using joint optical and near-infrared data. We present two transits of WASP-189b gathered simultaneously in the optical with HARPS and near-infrared with NIRPS, supported by photometric light curves from EulerCam and ExTrA. Transmission spectra were analysed via cross-correlation to detect absorption features and enhance the signal-to-noise ratio. Atmospheric retrievals quantified relative abundances by fitting overall metallicity and proxies for TiO, H$^-$, and e$^-$. Only atomic iron is detected in HARPS data (S/N ~5.5), but not in NIRPS, likely due to H$^-$ continuum dampening. Retrievals on HARPS-only and HARPS+NIRPS suggest the hydride-to-Fe ratio exceeds equilibrium predictions by about 0.5 dex, hinting at strong hydrogen ionisation. Including NIRPS data helps constrain H$^-$ abundance and set an upper limit on free electron density, unconstrained in HARPS-only data. These results emphasise H$^-$ as a significant continuum opacity source impeding detection of planetary absorption features in WASP-189b's near-infrared transmission spectrum. |
| title | Hydride ion continuum hides absorption signatures in the NIRPS near-infrared transmission spectrum of the ultra-hot gas giant WASP-189b |
| topic | Earth and Planetary Astrophysics |
| url | https://arxiv.org/abs/2507.21229 |